In an electrophotographic (EP) imaging process used in printers, copiers and the like, a photosensitive member, such as a photoconductive drum or belt, is uniformly charged over an outer surface. An electrostatic latent image is formed by selectively exposing the uniformly charged surface and applying toner. The toner is transferred to media where it becomes fixed by application of heat and pressure in a fuser assembly.
Fuser assemblies take many forms. They include hot rolls or belts and either presses against a backup roll to form a fusing nip. The assemblies operate at various temperatures and process speeds during imaging operations. Designers match materials of the rolls and belts to the thermal constraints of the system. Designs with high thermal conductivity and low thermal mass, for example, cause temperatures too high for fusing when media is not present at the fusing nip, as occurs before media arrives at the fusing nip and between adjacent sheets. Designs with high thermal conductivity, low density and low specific heat may also exhibit ‘hot offset’ upon imaging a leading portion of a first sheet of media at the fusing nip and ‘cold offset’ at the trailing portion during imaging the first sheet. ‘Hot offset’ is a condition whereby the toner sticks to the belts or rolls because the temperature of the fusing nip is overly hot. ‘Cold offset’ is a condition whereby the fusing temperature is relatively low and the toner does not fully melt and can easily rub or flake off the media. These conditions can also compound problems for imaging subsequent sheets of media in a same imaging operation. The inventors recognize the need for overcoming these problems, including a control algorithm to manage thermal phenomena before, during and after imaging the first sheet while minimizing poor fusing grade.